1. Field of the Invention
The present invention relates generally to the aft mounting system utilized by a gas turbine combustor transition piece. Specifically, the invention provides a support system for accurately mounting the transition duct to the turbine inlet section such that alignment adjustments between the transition duct and the turbine inlet can be made in multiple directions to the support system to compensate for thermal expansion and manufacturing and assembly tolerances.
2. Description of Related Art
Gas turbine ducts are traditionally utilized to direct hot gases from the combustor to the turbine inlet. Typically, for can-annular combustors, where each combustor centerline is not in direct line with the turbine inlet, this transition duct includes a period where change in flowpath geometry occurs in order to orient the hot combustion gases with the turbine inlet.
While this technique of redirecting combustor gas flow has been utilized for many years, increased demands for gas turbine output and improvement in combustor and turbine technology have allowed operating conditions to worsen, putting an even higher demand on the transition duct. These demands include higher operating temperature and pressure, which in turn induce higher mechanical, aerodynamic, and thermal loading.
Early support systems were comprised of gussets welded to the aft ends of the outer duct walls and to a base plate, which, in turn, was bolted to the turbine inlet frame. U.S. Pat. No. 3,759,038 issued to Scalzo, et al.; U.S. Pat. No. 3,750,398 issued to Adelizzi; and U.S. Pat. No. 3,609,968 issued to Mierley, Sr., et al, show examples of welded gusset support assemblies for transition ducts. A common shortfall of this design is the extremely high mechanical and thermal stresses seen in these fixed joints that can result in mechanical failure, as well as an inability to compensate for manufacturing and assembly tolerances between the combustor and turbine inlet.
Advancements from the fixed mount are pivoting mount systems as shown in U.S. Pat. No. 3,481,146 issued to Jackson, et al.; U.S. Pat. No. 2,457,619 issued to Buckland; U.S. Pat. No. 2,529,958 issued to Owner, et al.; and U.S. Pat. No. 2,511,432 issued to Feilden, discuss mounting systems for connecting flame tubes to turbine sections in which the mounting systems have limited pivoting capability tangential to a circle coaxial with the engine centerline. These linkage systems, while adequate for some thermal expansion and manufacturing and assembly tolerances, are limited to single pivot adjustments only.
A further advancement of a transition duct mounting system is disclosed in U.S. Pat. No. 4,422,288, which describes a hinge mount system for use in extreme temperature environments, where high thermal and mechanical loads exist. While this mounting system is an improvement over previous pivoting support systems, one problem of the system includes its limited range of mobility. With the ""288 configuration, the bracket is allowed to pivot only about one axis (one degree of freedom), the tangential direction relative to a circle with the center axis along the duct centerline, similar to the device described in U.S. Pat. No. 3,481,146. This movement is restricted by locking the mount down prior to installation by tightening the bolt and nut that runs through its pivot axis. While this mount is an improvement over fully fixed designs, such as gussets, for thermal and mechanical loads and over prior pivot mounts due to its fixed position to eliminate vibration concerns, it does not adequately satisfy positioning requirements of the transition duct to the turbine inlet to adjust for manufacturing and assembly issues.
The present invention, as disclosed below, allows the manufacturer or end user to adjust the position of the transition duct mount in three axes or directions to insure proper fit-up of the transition duct to the turbine section. While this position will be fixed during engine operation by a fastener, adjustments can be made prior to fixing the components in place or prior to engine installation if necessary. Thermal expansion during operation is accurately compensated to reduce system stress.
The present invention provides an aft mounting system for a transition duct and a turbine inlet that can be mounted together and adjusted in three degrees of freedom. The structural support system includes the capability of adjustment of the transition duct mating flange to the turbine inlet in three directions, as opposed to single axis adjustment that is currently available. The structural system in accordance with the present invention includes a central bracket with a central spherical ball mount that is affixed to the turbine inlet housing at one end and the transition duct at the opposite end, a dome plate that is affixed to the aft portion of the transition duct having mounting fingers, and a fastener that joins the central spherical ball mount to mounting fingers on the dome plate.
The central bracket includes a central spherical ball mount having a rigid, spherically-shaped body with a diametrical passageway configured in a predetermined double-conical shape. The passageway is conically tapered from the exact center of the sphere to the outer surface of the sphere. The conical passageway through the central spherical ball mount allows a predetermined amount of relative movement in three different directions or axial positions between the ball mount that is affixed to the turbine inlet housing and the dome plate that is affixed to the transition duct. The structural arrangement provides for three degrees of freedom between the transition duct and the turbine. The mounting dome affixed to the aft end of the transition duct includes a pair of mounting dome fingers. The spherical ball portion of the central spherical ball mount that is affixed to the turbine inlet is mounted in between washers and ring mounts, all of which are held in place by a fastener that passes through all the components and the conical ball joint passageway.
Therefore, in lieu of having a hinge joint with only a single direction or degree of freedom, the present invention provides for three different degrees of freedom, permitting relative movement and adjustment between the transition duct aft portion and the turbine inlet in three axes about the geometrical center of the central spherical ball mount portion of the bracket. The equivalence of motion would be equivalent to a Cartesian coordinate, X, Y, Z three-axis system that permits pitch, roll, and yaw about the axes center point. Therefore, using the present invention, the transition duct can be accurately affixed and attached to the turbine inlet section with greater ease, which allows for three different degrees of freedom of relative motion in the mounting structure. The size and contour of the conical passage diametrically through the ball joint relative to the diameter of the locking bolt defines the maximum distance of relative movement.
It is an object of the present invention to provide an improved mounting system for the aft end of a gas turbine combustor transition duct to the turbine inlet that provides three degrees of freedom of relative movement to compensate for manufacturing and assembly tolerances.
It is a further object of the present invention to provide an improved mounting system for the aft end of a gas turbine transition duct that is capable of withstanding extremely high operational temperature gradients and mechanical loads.
In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.